Range-finder or telemeter.



N0 MODEL.

PATENTED SEPT. 22, v1 903. A. BARR & W. STROUD.

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l W. W: 5 Zia flaw. W M MMMM PATENTEDSEPT. 22, .1903. A. BARR & w.STROUD. RANGE-FINDER 0R TELEMETER.

APPLICATION FILED MAR. 19, 1903. v

5 SHEETS-SHEET 2.

F0 MODEL.

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No. 739,475. PATENTED SEPT. 22, 1903. A. BARR & W. STROUD. RANGE FINDER0E TELEMETER.

APPLICATION FILED MAR. 19, N03.

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N0 MODEL.

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No. 739,4?5. 'PATENTBD SEPT. 22, 1903.

A. BARR & w. smonn.

RANGE FINDER OR TELEMETER.

5 SHEETS-SHEET 4.

APPLICATION FILED MAR. 19, 1903.

N0 MODEL.

PATENTBD SEPT 1. 22, 1903.

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NE Q3 A \m A. BARR & w. STROUD. "RANGE FINDEROR TELEMETER.

APPLICATION FILED MAR. 19, 1903.

N0 MODEL.

THE pawns FEYERSJZO. PNOTOJJTHOY. wsnmm'mn-me No. 739,475. fl' atentedSeptember 22, 1903.

UNITED ST TES PATENT OFFICE.

AROHIBALD BARR, OF GLASGOW, SCOTLAND, AND WILLIAM STROUD, OF

LEEDS, ENGLANDQ RANGE-FINDER R TELEMETER.

SPECIFICATION forming part of Letters Patent No. 739,475, datedSeptember 22, 1903.

Application filed March 19 1903. Serial No. 148,587. 7 (No model.)

To all whom it may concern.-

P and P are compound end reflectors con- Be 1t known that we, ARCHIBALDBARR,

stituting optical squares.

professor of engineering in the University of Glasgow, in the city ofGlasgow, Scotland, and

WILLIAM STROUD, professor of physics in the .Yorkshire College, Leeds,England, have inthe relative position of the partial images in thedirection of the base length as they appear in the field of view-21 e.,do not afiect What we call coincidence. To accomplish this, oneobjective only is used to transmit the two beams (instead of twoobjectives, as is customary) in combination with a separating-prism,which causes the partial im ages to appear separate and not overlapping.

A range-finder embodying our present improvements may be constructed inthe manner' described below and illustrated in the accompanyingdrawings. I Figure 1 is an elevation of the optical parts of ourrange-finder. Fig. 1 isa plan of the same. Fig. 2 is an elevation of themechanisms for effecting the movement of the oper-v ating refractoryprism D and the scale S. Fig. 2 is a plan of the same. Fig. 2 is a frontview of the fork F seen in Fig. 2. Fig. 2 is a section through thescale-drum S and shaft K, Fig. 2. Fig. 3 is an elevation of a mechanismfor effecting the halving adj ustment.

Fig. '3 is 'a plan of the same. Figs. 4 and 4 are respectively anelevation and plan of an astigmatizing-gear. Figs. 5 and 5 arerespectively an elevation and a plan of a complete instrument embodyingour invention. Figs. 6 and '6 are respectively a side and a plan view ofFig. 5, showing the end portions hinged and folded upon the centralportion.

0 is an objective, rectangular in form.

R is a right-angled prism acting by two reflections, as shown, as areturning-prism]? receiving the beam of light from the end reflector Pand reversing its direction, soas to cause it to pass through theobjective O'in the same general direction as that taken'by the beam fromthe end reflector P. As will be seen from Fig. 1, one of the beamspasses through the upper half of theobjective O,the'

other through the lower half.

transmittingface of which has in the front of it, cemented to it orformed upon it, a prism of small angle acting as a separating-prism todivide the partial images from each other. The prism Q is so placed thatthe separating edge E is in the focal plane of the objective 0, so thatthe partial images of an. object formed by light entering and reflectedby the end reflectors P and P are situated in the plane of theseparating edge. fusion in the diagram, only the central beams of lightare shown in Figs. 1 and l An eyepiece E Fig. 1-, is used to view theimages and the separating edge. One of the lenses of the eyepiece mayconveniently be cemented to or formed upon the second transmitting faceof the prism Q, as shown in the figure.

'D and D are two reflecting-prisms. One of these prisms-say D"is used asthe To avoid conoperating part of the optical system by being translatedalong the beam forming one of the partial images in conformity with themotion of the scale. The other prism D may be provided with means fortranslating it along the path of the other beam and so be used as an adjlisting-prism. H

The optical combination here illustrated has the property that motion ofthe various parts other than the deflecting-prisms does not aflect therelative positions of the partial images in respect'to coincidence.

Figs-2 and2 represent in elevation and plan the mechanisms for efleotingthe movement of the operating refracting-prismD and I the scale S. Thescale is graduatedin spiral form on a drum which is caused to. revolveIOO by operation of the working head H, accessible to the hand throughan aperture in the tube or case of the instrument. The holder M, whichcarries the retracting-prism D, is carried at N on the sleeve L, whichforms a nut on the screw K, and is prevented from rotating with thescrew by a fork F, attached to the nut N and engaging with a rod G,carried by the tube or frame-piece of the instrnment, as shown in Fig.2". The scaledrum S is free to rotate relatively to the nut, but isconstrained to move longitudinally with it, as shown at J in Fig. 2. Thescale-drum at its other end is feathered to the screwshaft K, so as tobe constrained to rotate with it, but to be free to slide along it, asshown in Fig. 2

It will be evident that when the working head H is rotated therefracting-prism D will be caused to move longitudinally and thescale-drum to rotate with but also to move longitudinally relatively tothe shaft K. If, then, the spiral on which the scale is out has the samepitch as the screw L, but the opposite hand, it will move so as to carrythe successive divisions of the scale past a fixed index I. The scalemay be so arranged as to be viewed through an eyepiece E by the left eyeafter the partial images have been brought into coincidence in the fieldof view of the right eyepiece E, as indicated in the drawings, Figs. 5and 5*.

The operation of the instrument is as follows: When a distant objectaflagpole, for instanceis viewed through the instrument, it is seenpartly above and partly below the separating edge,which appears as athin black line across the center of the field. The partial images will(usually) not appear in true alinement or coincidence, but one will beto the right of the other. When the working head H is rotated and theprism D is consequently translated, one of the partial images (the lowerone in the arrangement shown) is moved, and the scale is so graduatedthat when the partial images are brought into alinement-t'. e. when theyshow a continuous pole-the graduation on the scale which is opposite theindex-mark I will indicate the distance of the pole from the instrumentin yards or other unit.

We may use other means for eifecting the coincidence of the partialimages; but we prefer the refracting-prism method. We may use a straightscale instead of the spiral scale.

A lever U, which is supported from the tube or frame-piece of theinstrument by means of a spring V, carries the prism R by means of asuitable holder and is actuated at its other end by a screw of finepitch operated by a toothed head W. When the head W is rotated, theprism R is angled aboutahorizon- P, and thus the halving adjustment maybe effected-4. 6., one of the partial images may be moved verticallyrelatively to the other, so that when in alinement the partial imageswill form a complete image and not show duplication nor deficiency.

X is a plane cylindrical lens, through which both beams pass. When thelens is close up to the separating edge IE, it produces no appreciableeifect upon the images; but when by means of a motion of the lever Y(placed outside the tube of the instrument) the astigmatic lens iscarried. to some distance from the separating ed gethat is, to somedistance from the focal plane of the obj ective-the partial images areastigmatized-i. 6., they are drawn out vertically. By this means theobservation is facilitated in the case of an object that is too small orof too irregular a shape to be easily observed upon its natural form.

Instead of reflecting prisms of the type shown at P and P we may usereflectingprisms of any other known type that constitute opticalsquares, or we may use two plain mirrors fixed at forty-five degrees toeach other in the form of the ordinary optical square. In thisinstrument the end portions are hinged to the central portion forcompactness in carriage, as indicated in Figs. 6 and 6. This is notessential. The whole of the parts may be mounted in one continuous tube,or, again, the end portions may be made to come ed for convenience incarriage, or, again, the end portions may be arranged to slide ortelescope onto the central portion. This is rendered possible withoutderangement of the coincidence adjustment by the use of compoundreflectors forming optical squares at each end of the base. The centralportion may conveniently be made in the form of a box, with a bottomremovable for giving access to the working parts of the instrument. Atthe ends of the central portion windows may be fitted, as indicated inFigs. 5 and 5, to exclude dust or moisture when the parts are foldedover. Windows may also be fitted at the inner ends of the end portions.

1. A single-observer range-finder comprising a compound reflectorconstituting an optical square at each endof the base, areturning-prism,'a single objective to transmit the two beams, and aseparating-prism, substantially as described and illustrated on theaccompanying sheets of drawings.

2. A single-observer range-finder comprising a spiral scale which isrotated and translated by the operating mechanism of the instrument soas to indicate the range at a fixed index-mark placed within the tube orcase of the instrument and arranged to be read by one eye when theobservation has been made by the other eye, substantially as describedand illustrated on the accompanying sheets of drawings.

3. A single-observer range-finder compris ing a base-tube or frame-pieceformed in two or more parts, so as to be capable of being a. folded, orotherwise packed into a more convenient form when out of use,and havingcompound reflectors constituting optical squares at each end of thebase, substantially as describedand illustrated on the accompanying.

sheets of drawings.

Witnesses J OHN' LIDDLE, AGNES MACKINTOSH.

